WO2000039386A1 - Rubber reinforcing steel cord and heavy duty pneumatic radial tire using the steel cord - Google Patents

Abstract

A rubber reinforcing steel cord of bundle- and layer-twisted structure, wherein nine steel filaments are arranged around three steel filaments which are wave-formed two-dimensionally in longitudinal direction, and additional 14 steel filaments are arranged and twisted around a bundle-twisted cord formed by twisting all these steel filaments into one part; a heavy duty pneumatic radial tire, wherein the rubber reinforcing steel cord is used as carcass layer cords.

Description

 Akira Itoda

Steel cord for rubber reinforcement and pneumatic radial tire for heavy load using it

 Technical field

 TECHNICAL FIELD The present invention relates to a steel cord for reinforcing rubber which is excellent in rubber permeability and fatigue resistance and has high productivity, and a pneumatic radial tire for heavy load using the same as a cord for a carcass layer.

 Background technology

 Conventionally, heavy-duty pneumatic radial tires used in large vehicles such as trucks and buses are used as the code of the force layer that forms the tire frame in order to withstand heavy loads. Steel cords are often used.

As shown in Fig. 3, nine steel filaments 2 are twisted around the core of three steel filaments 1 as shown in Fig. 3. Twenty-five steel filaments 3 are twisted around steel filament 2 and wrapped around the outside, and constrained by 3 + 9 + 15 + W 1X12 + W or 27 with a layer-twisted structure like this, or 12 steel filaments twisted together and wrapped around the outside and constrained Twist the steel filament of the book and wrap the wrap filament around the outside to constrain it, such as 1 X 27 + W The bunched structure (bundle burning structure) is common. The wrap filament is for restraining the cord so that the cord does not vary.

 However, in the case of these layered or bunched steel cords, this wrap filament is present, and during use, this wrap filament and the steel filament immediately inside it are used. There was a problem in that fretting (rubbing) occurred between the steel cords and the steel filaments were strongly reduced, and as a result, the fatigue resistance of the steel cord was reduced.

In addition, since the steel cord having the layered combustion structure has a close-packed structure with no gap between the steel filaments, the rubber penetration into the cord is poor, and therefore, the steel cord has entered during use or storage of the tire. When moisture reaches this code, it causes corrosion of the code, which is a problem of poor corrosion fatigue resistance. On the other hand, the bunched steel cord has a smaller number of manufacturing steps than the layer stranded structure and can improve productivity.However, because it has a close-packed structure, rubber penetrates inside the cord. There was a problem of poor sex. Therefore, in recent years, in order to improve fretting and fatigue resistance, the number of outermost layers is more than the number of densest lines (the maximum number that can be arranged), although it has a three-layer structure as shown in Fig. 4. Reduce the outermost layer by one or two to increase the rubber permeability (Fig. 4 shows a 3 + 9 + 14 layer combustion structure), and restrict the cord with the permeated rubber. A steel cord without such a wrap filament has been proposed (JP-A-8-176977). However, in this steel cord, the inner layer other than the outermost layer has a close-packed structure, so rubber permeability is insufficient.

 Also, at least the core should have at least

A steel cord having a layer twist structure or a bunched structure using a steel filament having a single corrugated pattern has been proposed (Japanese Patent Application Laid-Open No. 9-31875). However, in this steel cord, although the rubber permeability is improved, the cord cross-sectional shape does not become a uniform perfect circle (it becomes distorted), so it is used as a carcass layer cord. When a large bending input is applied to the cable, uneven distortion is generated in the code and the fatigue resistance of the code is reduced. Figure 5 shows an example of this steel code. In Fig. 5, for example, one of the three cores is corrugated, and three steel filaments including this one are twisted around the core where nine steel filaments are twisted. Twist steel filament 2 and twist 14 steel filaments 3 around these 9 steel filaments 2 to obtain 3 Cr + 9 + 1 The steel cord has a layered combustion structure as shown in Fig. 4 (Cr means the crimp shape (wave shape)). The steel cord in Fig. 5 is twisted three times, which is disadvantageous in terms of manufacturing cost.

As other steel cords, for example, those shown in Figs. 6 and 7 have been proposed. In Figure 6, A total of 24 steel filaments 2 and 3 are arranged around three steel filaments 1 that are corrugated in the opposite direction, and all these steel filaments are placed once. The steel cord has a 3Cr / 4 punched structure that is twisted into a steel. In the steel cord shown in Fig. 6, the production process is high because the manufacturing process involves only one twist. However, since the cord cross-section is substantially triangular (straw-shaped), the strain is not uniform, so fatigue resistance is high. In addition, rubber permeability is insufficient because it has a close-packed structure. In Fig. 7, three steel filaments 1 shaped in a wave form in the longitudinal direction are combined with each other, and nine steel filaments 2 are wrapped around the aligned core without burning them together. Twisted, 14 steel filaments 3 are wrapped around the 9 steel filaments 2 to form a "Cr 19 + 14 layer fired steel coat". In the steel cord shown in Fig. 7, the core Cr is a straight plate, so a large tension load is applied to the core when the cord tension is applied. The tension distribution is uneven and fatigue resistance is not good.

 Disclosure of the invention

An object of the present invention is to provide a rubber reinforcing steel cord which is excellent in rubber permeability and fatigue resistance and has high productivity, and a pneumatic radial tire for heavy load using the steel cord as a carcass layer code. And there. In order to achieve this object, the rubber reinforcing steel cord of the present invention has nine steel filaments around three steel filaments corrugated two-dimensionally in the longitudinal direction. And all these steel filaments are bundled together at a time, and a further 14 steel filaments are arranged and twisted around the bundled cord. This is a steel cord with a bundled combustion + layer combustion structure, in which the diameter of the two-dimensionally corrugated steel filament is d, the waveform height is h, and the waveform pitch is P. Then, the parameter F represented by (h−d) ZP is in the relationship of 0.001 F ≤ 0.03, and the major diameter of the circumcircle of the cross section of the bundle twist cord is obtained. a and the minor axis b, bZa is 0.94 ≤ b / a ≤ 1.00, and the cross section of the steel cord is The ratio b of the 'short diameter b and' major axis a of the contact circle '/ a' is 0. 9 6 ≤ b '/ a' ≤ 1. Wherein the rubber element is a 0 0.

As described above, since all three steel filaments in the core are corrugated in the longitudinal direction, a gap is reliably secured in the core, so that the rubber permeability of the cord is reduced. It will be good. In addition, since the bundle has a core portion and a bundle-twisted structure, the cross-sectional shape of the steel cord can be made uniform and close to a perfect circle, so that a large bending input is applied to the steel cord. In this case, non-uniform distortion of the steel cord does not occur, resulting in reduced fatigue resistance of the steel cord. Nothing is done. Furthermore, the bundle twist + layer combustion structure reduces the number of manufacturing steps as compared to the layer combustion structure, so that productivity can be increased.

 In addition, heavy-duty pneumatic radial tires that use rubber reinforcing steel cord with excellent rubber permeability and fatigue resistance as the carcass layer code can increase durability. Become.

 BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a cross-sectional view of one example of a steel cord for rubber reinforcement according to the present invention.

 FIG. 2 is a series of side view explanatory diagrams of a steel filament constituting a core of a steel cord for rubber reinforcement of the present invention.

 FIG. 3 is a cross-sectional view of an example of a conventional steel cord for rubber reinforcement.

 FIG. 4 is a cross-sectional view of another example of a conventional steel cord for rubber reinforcement.

 FIG. 5 is a cross-sectional view of another example of a conventional steel cord for rubber reinforcement.

 FIG. 6 is a cross-sectional view of still another example of a conventional steel cord for rubber reinforcement.

 FIG. 7 is a cross-sectional view of still another example of the conventional steel cord for rubber reinforcement.

Figure 8 shows a steel filament book that constitutes the outermost layer. FIG. 3 is a cross-sectional view of an example of a rubber reinforcing steel cord having 13 pieces.

 BEST MODE FOR CARRYING OUT THE INVENTION

 As shown in FIG. 1, the steel cord 11 for rubber reinforcement according to the present invention has nine steel filaments 2 arranged around three steel filaments 1, and all of them are arranged. A bundle of 14 steel filaments 3 arranged around a twisted cord 10 made by twisting steel filaments at a time. + Layered structure (combustion structure of 3CrZ9 + l4).

 As shown in Fig. 2, each of the three steel filaments 1 in the core is shaped into a two-dimensional waveform in the longitudinal direction, and its diameter is d, and its waveform height is h, Assuming that the waveform pitch is P, the parameter expressed by (h-d) ZP-F has a relationship of 0.03.

 If F is less than 0.001 (0.001), the waveform will be shaped closer to the plate, and there will be no gap between the nine outer wires and rubber penetration. It becomes worse. When F exceeds 0.03 (F> 0.03), when cord tension acts, the distribution of tension between the core and the side becomes uneven, and fatigue resistance decreases. I will.

In the present invention, since the bundle has a core structure and a layer combustion structure, the steel cord has a uniform cross-sectional shape and a perfect circular shape. However, in order to obtain a more perfect circle, the ratio b / a of the major axis a to the minor axis b of the circumscribed circle of the cross section of the bundle twisted cord 10 should be 0.94. ≤ b Z a ≤ l. 0 0 and the ratio b '/ a' between the major axis a 'and the minor axis b' of the circumscribed circle of the cross section of steel cord 1 1 is 0.96 ≤ b '/ Let a '≤ 1.00. As a result, the fatigue resistance of the steel cord when a large bending input is applied to the steel cord 11 can be improved. In addition, by making the circular shape in this way, the arrangement of the steel filaments 1, 2, and 3 becomes axisymmetric in the cross section of the steel cord, so that the steel cord 11 has uneven distortion. Can be prevented from occurring.

 The number of steel filaments 3 constituting the outermost layer of the steel cord 11 shall be 14 less than the closest number (the maximum number that can be arranged, ie, 15). By using 14 pieces, a gap is created between the steel filaments in the outermost layer, making it easier for the rubber to penetrate inside. As a result, the wrap filament can be eliminated. If less than 14, for example 13 as shown in Figure 8, the diameter of the steel filament will be increased to maintain the required strength of the cord As a result, fatigue resistance is reduced, which is not preferable.

In addition, the steel filler constituting steel code 11 It is preferable that the wire diameter of each of the members 1, 2, and 3 be the same from the viewpoint of steel cord manufacturing cost. In addition, in terms of productivity and code shape, the twist pitch P of the bundled twisted cord 10 and a plurality of outermost layers arranged around the bundled twisted cord 10 are arranged. The burning pitch P of the ground 3 is P ₂ ≥ 2.5 + P! Good relationship. P ₂ <2.5 + P! In this case, the outermost layer of the filament is likely to fall into the bundle twisting cord 10, and the productivity is also deteriorated.

 Example, conventional example, comparative example

A steel pneumatic radial tire with a tire size of 1 000 R 20 14 PR was used by using a steel cord having the specifications shown in Tables 1 and 2 as the cord of the force layer (force code). The tires were manufactured (Examples 1 to 6, Conventional Examples 1 and 2, Comparative Examples 1 to 8), and the rubber permeability and fatigue resistance of these tires were evaluated. The results are shown in Tables 1 and 2. In Tables 1 and 2, the inside of the core 3 refers to the rubber permeability inside the core of the three clamps, and the space between the core 3 and the side 9 is the space between the three clamps and the nine sides. The rubber permeability and between the side 9 and the outermost sheath mean the rubber permeability between them, respectively. table 1

注） * 1 新品タイヤから取出した力一カスコー ドのゴム浸透率。

Note) * 1 Rubber penetration rate of force cascode extracted from new tires.

* Codes were taken from the new tires and tires after traveling 200,000 km, respectively, and a rotational bending fatigue test (under a constant stress) was performed to measure the number of times until breakage. (Value after running Z Value when new X 10 0 (%))

Table 2

注） * 1、 *2 表 1に同じ。

Note) * 1, * 2 Same as Table 1.

In Table 1, Example 6 is a case where P ₂ <2.5 + P, and in Example 6, the filament of the outermost layer falls into the bundle twisting cord, so that it is true. Circularity and rubber permeability slightly deteriorate. Also, in Table 1, Conventional Example 1 is a case where a steel cord having a 3 + 9 + 15 + W layer twisted structure as shown in Fig. 3 is used, and Conventional Example 2 is as shown in Fig. 4. This is the case where a steel cord with a 3 + 9 + 14 layer twist structure is used.

In Table 2, Comparative Example 1 is a case in which a steel cord having a layer combustion structure of 3 Cr + 9 + 14 as shown in FIG. 5 is used, and Comparative Example 2 is a case in which a 3 Cr as shown in FIG. 6 is used. r The steel cord with the layered structure of Z24 was used.Comparative Example 3 used the steel cord with the layered structure of ¥ Cr19 + 14 as shown in Fig. 7. It is. Comparative Example 4 uses a steel cord having a 3CrZ9 + 14 layer-twisted structure as shown in Fig. 1, but the parameter F is too small. Although a steel cord with a 3C r / 9 + l 4 layered structure as shown in Fig. 1 was used, but the parameter F was too large, the comparative example 6 showed a 3C as shown in Fig. 1. In this case, the roundness bZa is too small, although the steel cord with rZ9 + 14 layer combustion structure is used.Comparative Example 7 shows 3CrZ9 as shown in Fig. 1. In the case where the steel cord with a layered structure of +14 was used but the roundness b Z a and the wedge '/ a' were both too small, Comparative Example 8 This is the case where a steel cord with a 3Cr / 9 + 13 layer combustion structure as shown in Fig. 1 is used.

 As is clear from Tables 1 and 2, Examples 1 to 6 according to the present invention are superior in both rubber permeability and fatigue resistance as compared with Conventional Examples 1 and 2 and Comparative Examples 1 to 8. You can see that it is.

 As described above, the steel cord for rubber reinforcement of the present invention has nine steel filaments arranged around three stainless steel filaments two-dimensionally corrugated in the longitudinal direction. Then, around a bundle twisted cord made by twisting all of these steel filaments at once, a bundle of 14 steel filaments is arranged and then bundled together. A steel cord with a + layer combustion structure, where d is the diameter of the two-dimensionally corrugated steel filament, h is the height of the waveform, and P is the waveform pitch. The parameter F expressed by ZP is 0.01 ≤ F ≤ 0.03, and the major axis a and minor axis b of the circumcircle of the cross section of the bundled fuel cord The ratio b Z a is 0.94 ≤ ha ≤ 1.00, and the length of the circumcircle of the cross section of the steel cord The ratio of a 'to minor axis b' b '/ a' force 0.96 ≤ b'Za '≤ 1.00 increases rubber permeability, fatigue resistance, and productivity This is possible.

Further, in the steel cord for rubber reinforcement of the present invention, (a) the three steel filaments at the core are not aligned but Since it is twisted together with the nine outer sheaths, the tension load does not concentrate on the core when tension is applied to the steel cord (does not shift). (B) The number of steel filaments in the outermost layer By reducing the diameter to the minimum necessary, the filament wire diameter does not increase (good fatigue resistance), and (c) the lap filament can be removed because of good rubber permeability. There are advantages such as becoming. -i

 Four

 In addition, by using this steel cord for rubber reinforcement as a cord for the carcass layer of a pneumatic radial tire for heavy loads, the durability of the pneumatic radial tire for heavy loads can be increased. Becomes

Claims

The scope of the claims  1. Nine steel filaments are arranged around three steel filaments that are two-dimensionally corrugated in the longitudinal direction, and all of these steel filaments are combined at once. A steel cord with a bundle twist + layer combustion structure in which 14 steel filaments are arranged and wrapped around the bundled bundled cord If the diameter of the two-dimensionally corrugated steel filament is d, the height of the waveform is h, and the pitch of the waveform is P, the parameter F represented by (h-d) ZP Are in the relationship of 0.001 ≤ F ≤ 0.03, and the ratio bZa between the major axis a and the minor axis b of the circumcircle of the cross section of the bundle twisting cord is 0.94 ≤ h / a ≤ \ .0.00, and the ratio b '/ a' between the major axis a 'and the minor axis b' of the circumscribed circle in the cross section of the steel code is 0.96 ≤ b '/ a '≤ 1. 0 0 Steel cord for rubber reinforcement. 2. The Taba燃Ri code for twisting pitch P and the bundle twist co -. 1 four and off I la e n t twist pin Tutsi P ₂ which is arranged around the soil, P ₂ ≥ 2 5 The steel cord for rubber reinforcement according to claim 1, wherein the steel cord has a relationship of + P ,.  3. A pneumatic radial tire for heavy loads, wherein the steel cord for rubber reinforcement according to claim 1 or 2 is used as a carcass layer code.